1. Field
This disclosure relates to predictive motion tracking for a head mounted display.
2. Description of the Related Art
Head mounted displays have long been used in virtual reality and augmented reality systems. Virtual reality systems, typically, envelop a wearer's eyes completely and substitute a “virtual” reality for reality. These virtual reality environments maybe crude, either intentionally or through lack of capability of the virtual reality system. However, virtual reality environments may also be detailed, interactive and quite complex, involving virtual people, conversations and experiences. The most obvious exemplar of a virtual environment may be a video game involving a player character interacting with a game world. However, virtual environments need not be games and may, instead, be educational experiences, group activities (such as a tour of a historical site), or merely sitting in a virtual room with an avatar representative of a friend and carrying on a conversation.
Augmented reality systems, in contrast, typically provide an overlay semi-transparent or transparent screen or screens in front of a wearer's eyes such that reality is “augmented” with additional information, graphical representations, or supplemental data. Augmented reality may, for example, superimpose “virtual” people, items, cars, rooms, spaces, signs and other data over reality to a viewer. Simple augmented reality systems may simply provide information regarding the scene or area being viewed (e.g. temperature, upcoming appointments for a wearer, speed of movement, GPS location, etc.). More complex augmented reality systems may superimpose “virtual” tangible objects onto a scene, such as walls, artwork, individuals and similar elements. These may update, in real-time so that images presented on the augmented reality display appear to be present within a location to a wearer.
In either system, the movement of a wearer of such a headset may be tracked in order to react to user movements and update the images being presented. This tracking utilizes sensors, such as gyroscopes, accelerometers, magnetometers, and, in some cases, cameras or color sensors that generate data pertaining to position, motion, and orientation of a headset. This tracking data can be used to generate information such as angular velocity, linear acceleration, and gravitational data that may in turn be used to adjust the display of the headset in response to wearer movement.
Predictive movement has been incorporated into virtual reality and augmented reality headsets in the past. However, sample rates for the sensors identified above have typically been quite long—on the order tens of milliseconds—relative to the acuity of human vision. Because the time between samples is long, these predictions often result in so-called “overshoot” where a prediction overshoots the actual head position and orientation or must be smoothed so severely to avoid other problems that they result in predictions sufficiently inaccurate that merely not predicting movement delivers better results.
Throughout this description, elements appearing in figures are assigned three-digit reference designators, where the most significant digit is the figure number and the two least significant digits are specific to the element. An element that is not described in conjunction with a figure may be presumed to have the same characteristics and function as a previously-described element having a reference designator with the same least significant digits.